Positively working photosensitive materials which are solubilized by irradiation with actinic rays include orthoquinonediazide compounds. The orthoquinonediazide compounds have been widely used in practice for the production of lithographic printing plates, photoresists, and the like. References can be made to it in many publications, e.g., U.S. Pat. Nos. 2,766,118, 2,767,092, 2,772,972, 2,859,112, 2,907,665, 3,046,110, 3,046,111, 3,046,115, 3,046,118, 3,046,119, 3,046,120, 3,046,121, 3,046,122, 3,046,123, 3,061,430, 3,102,809, 3,106,465, 3,635,709, 3,647,443, etc.
These conventional orthoquinonediazide compounds are decomposed upon irradiation with actinic rays to produce carboxylic acids of 5-membered rings, whereby they become alkali-soluble. Owing to this property, they serve as positively working photosensitive materials, but they also have a defect of insufficient photosensitivity. This arises from the fact that the quantum yield in the photochemical reaction of the orthoquinonediazide compounds does not essentially exceed 1.
Although many attempts have been made to enhance photosensitivity of photosensitive compositions containing the orthoquinonediazide compounds, it has been very difficult to increase photosensitivity of such compositions while retaining their development latitudes. Examples of such attempts are described in U.S. Pat. Nos. 3,661,582, 4,009,003, 4,307,173, etc.
Recently some photosensitive compositions which can work positively without containing orthoquinonediazide compounds have been proposed. One of such compositions is the one containing a polymer compound having an orthonitrocarbinol ester group as disclosed in U.S. Pat. No. 3,849,137. The photosensitivity of this composition is, however, still insufficient for the same reason as in the case of the compositions containing the orthoquinonediazide compounds.
Aside from the above-described methods, there have been proposed a method of enhancing photosensitivity by using a photosensitive system which can be activated by catalytic action, in which application is made of an acid produced upon photolysis inducing a second reaction to thereby solubilize the exposed areas.
Examples of such a photosensitive system include combinations of a compound capable of producing an acid upon photolysis with an acetal or O,N-acetal compound (U.S. Pat. No. 3,779,778), an orthoester or amidoacetal compound (U.S. Pat. No. 4,101,323), a polymer having an acetal or ketal group in its main chain (U.S. Pat. No. 4,247,611), an enol ether compound (U.S. Pat. No. 4,248,957), an N-acyliminocarboxylic acid compound (U.S. Pat. No. 4,250,247), a polymer having an orthoester group in its main chain (U.S. Pat. No. 4,311,782), a silyl ester compound (Japanese Patent Application (OPI) No. 10427/85, the term "OPI" herein used means "unexamined published application") or a silyl ether compound (Japanese Patent Application (OPI) No. 37549/85). These combinations have a possibility of exhibiting high photosensitivities because they have, in principle, quantum yields higher than 1. However, in the case of the systems containing the acetal or O,N-acetal compound or the polymer having an acetal or ketal group in its main chain, the second reaction caused by the acid produced upon photolysis proceeds so slowly that photosensitivity high enough to be suitable for practical use cannot be achieved. On the other hand, in the cases of the systems containing the orthoester or amidoacetal compound, the enol ether compound or the N-acyliminocarboxylic acid compound, photosensitive attained are undoubtedly high, but these compounds are poor in stability with a lapse of time and cannot be preserved for a long period of time. Further, the combination with the polymer having an orthoester group in its main chain, though highly photosensitive, suffers from the disadvantage of a narrow development latitude. The combinations with the silyl ester compound or the silyl ether compound exhibit higher sensitivities and high stability with time as compared with other compounds and polymers, but the stability with time is still insufficient for practical use.